If you’re looking at a web camera, just about any USB camera will work. I’m currently using a cheap Logitech C310, which has both camera and microphone.
If you’re looking for a high quality audio device instead of a camera, I have always had good experience with Jabra’s devices. I currently use a Jabra Speak 410 on my work computer. (I use it’s built-in camera for video, but it’s built-in microphone is terrible.)
The Jabra devices have really good quality, but they are a bit expensive. In my case, my employer paid for it, but I still think they are worth the price.
A webcam will solve your camera and microphone problem. I have had great luck with Logitech webcams.
For Mac mini audio, try a HomePod mini. It not only makes a fine speaker but is great as a speakerphone for calls, and handles all manner of Siri requests.
+1 for Logitech’s cameras. I have their Streamcam which has 60fps HD which is nice and smooth but my wife is happy with her 30fps C310. Their built in mic is good but I’ve long used a Yeti X for audio and it is excellent. It depends on how important quality is there for you, if you teach for example or regularly speak to a lot of people or record podcasts, a dedicated mic brings a lot. But the webcam mic is fine for Zoom chats. I agree with Julio, hard to argue with the choice of a HomePod Mini as a speaker, so surprisingly good.
As far as I’m aware, no, there’s no way to use a HomePod for audio input to a Mac. You can use it as an input for phone calls as well, but nothing Mac-related.